Multi-level metallization is a critical area of concern in advanced semiconductor fabrication where designers continue to strive for circuit density maximization. Metallization interconnect techniques typically require electrical connection between metal layers or runners occurring at different elevations within a semiconductor substrate. Such is typically conducted, in part, by etching a lower contact opening through insulating materials to a lower elevation metal layer. Increased circuit density has resulted in narrower and deeper electrical contact openings between the layers within the substrate, and thus have provided increased challenges to the circuit designer.
In making electrical contact, for example, to an active silicon substrate area, prior art practice typically has included forming an insulating layer over the active area. Following the deposit of the insulating layer, photoresist is deposited and patterned. The photoresist is subsequently exposed and stripped to define an aperture in the photoresist where a contact opening to the active area is desired. The insulating layer is then anisotropically etched relative to the photoresist to define a contact opening through the insulating layer.
While the prior art processes work with various degrees of success, they have shortcomings which have detracted from their usefulness. For example, the prior art technique has resulted in a tendency to damage the silicon substrate. Still further, deep and narrow contact openings are often very difficult to fill by conventional deposition techniques such as sputtering.
An electrical contact, and method for forming an electrical contact which addresses these and other problems is the subject matter of the present invention.